The present invention pertains to a method and an apparatus for imparting a desired shape to a cylindrical object such as a component of a smoke filter or other smoking apparatus. More particularly, it pertains to a method and apparatus for providing deformations of any desired shape in such an object, preferably by means of a combination of pressure and heat.
Cigarette filters comprising a cylindrical rod of cellulose acetate or another suitable filtering material are well known. The filtration of the tobacco smoke can be made more efficient by providing grooves of various shapes and sizes in the exterior peripheral surface of the filter rod. For example, U.S. Pat. No. 3,811,451, issued May 21, 1974, to Berger for a Tobacco Smoke Filter, discloses a filter of cellulose acetate containing a pouch filled with a more highly sorbent material such as activated charcoal, and having a plurality of longitudinal flutes which extend the greater part of the length of the filter from one end thereof.
U.S. Pat. No. 4,022,221, also to Berger, discloses a filter having, in one embodiment, a plurality of longitudinal flutes or grooves formed in the axially central portion of the external surface thereof. In another embodiment, the flutes extend from the end of the filter adjacent the tobacco rod to a point near the mouth end of the filter, and in a third embodiment, a helical groove is provided in the peripheral surface of the filter.
U.S. Pat. No. 3,768,489, issued Oct. 30, 1973, to Kiefer et al., for a Tobacco Smoke Filter, discloses a filter of cellulose acetate or the like, the filtration characteristics of which are improved by the provision of two longitudinal grooves in the exterior of the filter. The two grooves are located diametrically opposite each other and are axially offset from each other. In another embodiment, the two flutes are axially aligned with each other, and the ends of the filter are cut oblique to the axis thereof. In a third embodiment, a plurality of circumferentially adjacent grooves are provided on each side of the filter, and in a fourth embodiment a sectoral recess is formed on each side of the filter in place of the grooves.
The disclosures of U.S. Pat. Nos. 3,768,489, 3,811,451 and 4,022,221 are incorporated herein by reference.
Various methods for forming grooves, flutes, and other external deformations in filters are known. For example, in U.S. Pat. No. 3,811,451, the flutes are formed by means of crimping. In U.S. Pat. No. 4,022,221, it is similarly contemplated to form the flutes by means of crimping wheels such as those shown therein.
U.S. Pat. No. 4,164,438, issued Aug. 14, 1979, to Lebet for a "Method of Making Transverse Flow of Cigarette Filters", discloses a method and apparatus for forming grooves on opposite sides of a filter plug.
The filter plugs are first heated by exposure to high temperature water vapor or by means of high frequency electromagnetic radiation, for example, to plasticize the cellulose acetate of which they are made. After being heated, the filter plugs are shaped by means of a device comprising three drums rotating about parallel axes. Each of the drums has grooves formed in its peripheral surface parallel to its axis to receive the filter plugs.
Each filter plug is initially fed while in a heated state to the first drum, which receives it in a peripheral groove and carries it to the point where the first and second drums are closest. The gap between the first and second drums is quite small, and as the filter plug reaches the point it is deformed by an indenter disposed in a peripheral groove of the second drum, the first drum serving as a counterpunch. As the filter plug is deformed in this manner, it is simultaneously transferred from the first to the second drum, which then conveys it to the third drum, on which indenters are also disposed. As the filter plug reaches the gap between the second and third drums, it is deformed a second time by one of the indenters on the third drum. The second drum acts as a counterpunch for this process.
After the filter plug is punched for the second time, it remains on the second drum, which carries it to a fourth drum that removes it from the second drum by means of suction and then releases it into a discharge chute.
By this method, the filter rod is shaped by a series of very quick punching operations each of which is performed by a punch disposed on one drum while another drum, carrying the filter plug, serves as a counterpunch. In order for the desired shape to be impressed on a filter plug satisfactorily, the portion of the surface that is to be deformed must be in contact with the heated forming element for a certain minimum period of time which is a function of the filter plug material. Accordingly, the short time allotted by Lebet to form each groove in the filter plug would make it impossible to shape filter plugs at an acceptable speed.
Another method and apparatus for shaping filter rods are disclosed in U.S. Pat. No. 4,149,546, issued Apr. 17, 1979, to Luke et al. for the "Production of Tobacco-Smoke Filters". This patent discloses using a rotating drum to move the filter plugs past a stationary heated forming unit defined by the inner surface of an arcuate stator positioned adjacent the peripheral surface of the drum and spaced a uniform distance therefrom. The filter plugs are borne by the drum in a manner that permits them to rotate about their own longitudinal axes. The rotation of the drum carries each filter plug along the length of the stator. As this occurs, the filter plug, being free to rotate, rolls along the inner surface of the stator, the shape of which is imparted to the filter plug.
It is believed to be impossible, using the method disclosed by Luke et al., to shape filter plugs satisfactorily at a rate of more than 200-300 filter plugs per minute. Since a cigarette maker routinely produces about 4,000 cigarettes per minute, this low rate is unacceptable. The problem is believed to be that, using the method, the filter plugs remain in contact with the heated forming element a sufficient length of time to be properly shaped only if the drum is rotated at a relatively slow speed.
U.S. Pat. No. 3,483,873, issued Dec. 16, 1979, to Hinzmann, for an "Apparatus for Making Holes in Tobacco Rods or the like", discloses an apparatus in which holes are formed in a tobacco rod by means of pins provided in the periphery of a drum about which the tobacco rods are rolled by means of an adjacent endless belt.
It is accordingly the principal object of the invention to provide a method and an apparatus for forming cylindrical articles such as smoke filter components without the disadvantages of the prior art.
It is more particularly the object of the invention to provide a method and an apparatus with which cigarette filter components can be formed at a rate similar to that at which cigarettes can be manufactured by a cigarette making machine.